This project involves intracellular recordings from photoreceptor, horizontal, and bipolar cells in an in vitro preparation of mammalian retina. An arterially-perfused eyecup preparation of the eastern gray (tree) squirrel, Sciurus carolinensis, has been developed in this laboratory for this purpose. We have begun to study the response characteristics of these retinal neurons, and have most fully characterized horizontal cell types. In our analyses, we will study the spectral sensitivites, intensity-response characteristics, flash sensitivities, response time courses, and receptive field properties of these cells. We are particularly interested in studying the nature and extent of interactions between photoreceptors, and between photoreceptors and horizontal cells. In addition, we propose to correlate the physiology and morphology of these cells by injecting all studied cells with horseradish peroxidase and studying appropriate morphological characteristics.